When
results from sub-groups of a CARAVAN sample appear in the detailed tabulations,
an indicator of statistically significant differences is added to the tables run
on our standard demographic banners.The
test is performed on percentages as well asmean values.Each sub-sample is assigned a letter.When the percentage of one sub-sample is significantly
different from the percentage of another sub-sample, the letter representing one
of the two samples appears next to the percentage (or mean) of the other sample.

For
instance the percentage of males answering yes to a particular question may be
compared to the percentage of females answering yes to the same question.In the example below, the male sample is assigned the letter B, and the
female sample is assigned the letter C.Here,
respondents were asked whether a certain business practice is acceptable.67% of women said that it was -- a proportion significantly greater than
the 57% of males who believe that the practice is acceptable.To indicate that women are significantly more likely to find the practice
acceptable than are men, the letter B -- the letter assigned to the male
sub-sample -- appears next to the 67% in the female column.Similarly, the 37% of men that find the practice unacceptable is
significantly greater than the 29% of women who do so and, therefore, the letter
C -- the letter assigned to the female sub-sample -- appears next to the
37% in the male column.

Acceptability
of [practice]

Sex

Total

Male

Female

(A)

(B)

(C)

Unweighted
Total

977

488

489

Weighted
Total

967

464

503

Acceptable

611

274

337

63%

59%

67%B

Not
Acceptable

319

171

148

33%

37%C

29%

Dont
Know

37

18

19

4%

4%

4%

Significance
testing is done to the 95% confidence level.The columns compared are listed at the bottom of each table.

A
number of factors need to be considered when determining which type of t-test
should be applied, such as whether the samples being compared overlap, whether
they are means or percentages, etc.Opinion
Research Corporation's software has the capability to perform the appropriate
test.

Note
that any statistical test becomes less reliable when the sample sizes are small.Even though the test mathematically can be performed on samples as low as
thirty, sixty respondents is the reasonable lower bound on the size of the
sample.